The stratigraphy and depositional environment of the Aphebian Snyder Group, Labrador

1978 ◽  
Vol 15 (1) ◽  
pp. 52-68 ◽  
Author(s):  
J. Alexander Speer
Keyword(s):  
Thin Sheet ◽  
Water Environment ◽  
Contact Metamorphism ◽  
Iron Formation ◽  
The North ◽  
Fine Grain ◽  
Lithostratigraphic Units ◽  
High Maturity ◽  
Lenticular Bedding ◽  
Shelf Sedimentation

The Snyder Group is an Aphebian sedimentary sequence unconformably overlying Archean rocks that has undergone deformation and a medium to high grade contact metamorphism as the result of the emplacement of the Elsonian Kiglapait intrusion. Five lithostratigraphic units totaling 239 m in thickness have been recognized; in ascending order they are: (1) a lower quartz arenite with local arkosic arenites, pelites, conglomerates and a discontinuous basal conglomerate; (2) a manganiferous silicate iron formation; (3) a marble with associated calc-silicates and quartzites; (4) a sphalerite- and pyrrhotite-bearing quartz-rich, graphitic siltstone; and (5) an upper quartzite. The several intrusive rocks are largely basic and intermediate in composition and are grouped as being emplaced either before or after the contact metamorphism by the Kiglapait intrusion. Collectively, their sills and dikes have expanded the section to 355 m.The lower and upper quartzites with their high maturity; poly modal festoon, trough crossbedding; reactivation surfaces; flaser and lenticular bedding; ripple marks; graded bedding; and conglomerates were probably deposited on a shallow, subtidal, tide- and current-dominated sand flat dissected by tidal channels. The few metapelites record deposition during an occasional less turbulent environment. The fine grain size, intraformational conglomerates, cross-laminations, and thin laminations of the intermediate formations indicate that they were deposited in a quiet, probably shallow water environment disturbed only by occasional storms. The sedimentary structures, lithologies and thin, sheet geometries of the beds suggest that the Snyder Group represents a siliciclastic sea shelf sedimentation, which, if reconstructions of the North Atlantic craton are correct, was epicontinental.

A new volcanic province: evidence from glacial erratics in western North Greenland

2000 ◽  
pp. 35-41 ◽  
Author(s):  
Peter R. Dawes ◽  
Bjørn Thomassen ◽  
T.I. Hauge Andersson
Keyword(s):  
Volcanic Rocks ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Common Component ◽  
Volcanic Province ◽  
North West ◽  
North East ◽  
The North ◽  
Surficial Deposits ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Dawes, P. R., Thomassen, B., & Andersson, T. H. (2000). A new volcanic province: evidence from glacial erratics in western North Greenland. Geology of Greenland Survey Bulletin, 186, 35-41. https://doi.org/10.34194/ggub.v186.5213 _______________ Mapping and regional geological studies in northern Greenland were carried out during the project Kane Basin 1999 (see Dawes et al. 2000, this volume). During ore geological studies in Washington Land by one of us (B.T.), finds of erratics of banded iron formation (BIF) directed special attention to the till, glaciofluvial and fluvial sediments. This led to the discovery that in certain parts of Daugaard-Jensen Land and Washington Land volcanic rocks form a common component of the surficial deposits, with particularly colourful, red porphyries catching the eye. The presence of BIF is interesting but not altogether unexpected since BIF erratics have been reported from southern Hall Land just to the north-east (Kelly & Bennike 1992) and such rocks crop out in the Precambrian shield of North-West Greenland to the south (Fig. 1; Dawes 1991). On the other hand, the presence of volcanic erratics was unexpected and stimulated the work reported on here.

scholarly journals 3D lithostratigraphic model of the Paleogene of the onshore part of the Moesian Platform (Northeast Bulgaria)

2018 ◽  
Vol 47 (1) ◽  
pp. 23-36
Author(s):  
Boris Valchev ◽  
Dimitar Sachkov ◽  
Sava Juranov
Keyword(s):  
Spatial Distribution ◽  
Sedimentary Rocks ◽  
Eastern Slope ◽  
The South ◽  
The North ◽  
Lithostratigraphic Units ◽  
Moesian Platform ◽  
Regional Tectonic ◽  
Model Database ◽  
The Individual

The Paleogene sedimentary rocks in the north-easternmost part of the territory of Bulgaria have been penetrated by numerous boreholes. In terms of regional tectonic zonation, the study area is a part of the onshore sector of the Moesian Platform, which partly includes the South Dobrogea Unit and the easternmost part of the North Bulgarian Dome with its eastern slope. The lithostratigraphy of the Paleogene successions consists of six formal units (the Komarevo, Beloslav, Dikilitash, Aladan, Avren, and Ruslar formations) and one informal unit (glauconitic marker). For compiling an overall conception of the regional aspects (lithology, thickness, spatial distribution, and relationships) of the individual lithostratigraphic units and for illustration of their spatial distribution, a 3D lithostratigraphic model based on reinterpretation of individual borehole sections has been created. The model database was compiled by integration of the original lithological data from 338 borehole sections.

scholarly journals A revised lithostratigraphy for the Palaeogene – lower Neogene of the Danish North Sea

2005 ◽  
Vol 7 ◽  
pp. 21-24
Author(s):  
Poul Schiøler ◽  
Jan Andsbjerg ◽  
Ole R. Clausen ◽  
Gregers Dam ◽  
Karen Dybkjær ◽  
...  
Keyword(s):  
North Sea ◽  
Energy Agency ◽  
Sequence Stratigraphic ◽  
Oil Companies ◽  
The North ◽  
Reference Sections ◽  
Stratigraphic Model ◽  
Lithostratigraphic Units ◽  
The North Sea ◽  
Stratigraphic Nomenclature

Intense drilling activity following the discovery of the Siri Field in 1995 has resulted in an improved understanding of the siliciclastic Palaeogene succession in the Danish North Sea sector (Fig. 1). Many of the new wells were drilled in the search for oil reservoirs in sand bodies of Paleocene–Eocene age. The existing lithostratigraphy was based on data from a generation of wells that were drilled with deeper stratigraphic targets, with little or no interest in the overlying Palaeogene sediments, and thus did not adequately consider the significance of the Palaeogene sandstone units in the Danish sector. In order to improve the understanding of the distribution, morphology and age of the Palaeogene sediments, in particular the economically important sandstone bodies, a detailed study of this succession in the Danish North Sea has recently been undertaken. An important aim of the project was to update the lithostratigraphic framework on the basis of the new data.The project was carried out at the Geological Survey of Denmark and Greenland (GEUS) with participants from the University of Aarhus, DONG E&P and Statoil Norway, and was supported by the Danish Energy Agency. Most scientific results cannot be released until September 2006, but a revised lithostratigraphic scheme may be published prior to that date. Formal definition of new units and revision of the lithostratigraphy are in preparation. All of the widespread Palaeogene mudstone units in the North Sea have previously been formally established in Norwegian or British wells, and no reference sections exist in the Danish sector. As the lithology of a stratigraphic unit may vary slightly from one area to another, Danish reference wells have been identified during the present project, and the lithological descriptions of the formations have been expanded to include the appearance of the units in the Danish sector. Many of the sandstone bodies recently discovered in the Danish sector have a limited spatial distribution and were sourced from other areas than their contemporaneous counterparts in the Norwegian and British sectors. These sandstone bodies are therefore defined as new lithostratigraphic units in the Danish sector, and are assigned Danish type and reference sections. There is a high degree of lithological similarity between the Palaeogene–Neogene mudstone succession from Danish offshore boreholes and that from onshore exposures and boreholes, and some of the mudstone units indeed seem identical. However, in order to acknowledge the traditional distinction between offshore and onshore stratigraphic nomenclature, the two sets of nomenclature are kept separate herein. In recent years oil companies operating in the North Sea have developed various in-house lithostratigraphic charts for the Paleocene–Eocene sand and mudstone successions in the Danish and Norwegian sectors. A number of informal lithostratigraphic units have been adopted and widely used. In the present project, these units have been formally defined and described, maintaining their original names whenever feasible, with the aim of providing an unequivocal nomenclature for the Palaeogene – lower Neogene succession in the Danish sector. It has not been the intention to establish a sequence stratigraphic model for this succession in the North Sea; the reader is referred to the comprehensive works of Michelsen (1993), Neal et al. (1994), Mudge & Bujak (1994, 1996a, b), Michelsen et al. (1995, 1998), Danielsen et al. (1997) and Rasmussen (2004).

scholarly journals A Mesoproterozoic iron formation

2018 ◽  
Vol 115 (17) ◽  
pp. E3895-E3904 ◽  
Author(s):  
Donald E. Canfield ◽  
Shuichang Zhang ◽  
Huajian Wang ◽  
Xiaomei Wang ◽  
Wenzhi Zhao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Time Window ◽  
Iron Formation ◽  
The North ◽  
Fe Oxidation ◽  
Organic Biomarkers ◽  
Rock Eval ◽  
Fe Reduction ◽  
Rule Out ◽  
Xiamaling Formation

We describe a 1,400 million-year old (Ma) iron formation (IF) from the Xiamaling Formation of the North China Craton. We estimate this IF to have contained at least 520 gigatons of authigenic Fe, comparable in size to many IFs of the Paleoproterozoic Era (2,500–1,600 Ma). Therefore, substantial IFs formed in the time window between 1,800 and 800 Ma, where they are generally believed to have been absent. The Xiamaling IF is of exceptionally low thermal maturity, allowing the preservation of organic biomarkers and an unprecedented view of iron-cycle dynamics during IF emplacement. We identify tetramethyl aryl isoprenoid (TMAI) biomarkers linked to anoxygenic photosynthetic bacteria and thus phototrophic Fe oxidation. Although we cannot rule out other pathways of Fe oxidation, iron and organic matter likely deposited to the sediment in a ratio similar to that expected for anoxygenic photosynthesis. Fe reduction was likely a dominant and efficient pathway of organic matter mineralization, as indicated by organic matter maturation by Rock Eval pyrolysis combined with carbon isotope analyses: Indeed, Fe reduction was seemingly as efficient as oxic respiration. Overall, this Mesoproterozoic-aged IF shows many similarities to Archean-aged (>2,500 Ma) banded IFs (BIFs), but with an exceptional state of preservation, allowing an unprecedented exploration of Fe-cycle dynamics in IF deposition.

The ghost bat in the Pilbara: 100 years on.

2000 ◽  
Vol 22 (2) ◽  
pp. 93 ◽  
Author(s):  
KN Armstrong ◽  
SD Anstee
Keyword(s):  
Western Australia ◽  
New Records ◽  
Iron Formation ◽  
Natural Habitats ◽  
The Third ◽  
North East ◽  
The North ◽  
Preferred Habitat

This paper summarises the roost habitat and distribution of the ghost bat, Macroderma gigas (Dobson, 1880), in the Pilbara region of Western Australia, with particular emphasis on natural habitats. The preferred habitat of M. gigas in the Hamersley Ranges appears to be caves beneath bluffs of low rounded hills composed of Marra Mamba geology. Habitats were also found in the larger hills of Brockman Iron Formation in the Hamersley Range, and other formations beneath bluffs composed of Gorge Creek Group geology to the north east. Granite rockpiles are also used in the eastern Pilbara. A summary of Pilbara records from numerous sources is presented, including anecdotal accounts and other new records. This includes a newly discovered maternity site from the Hamersley Ranges, only the third reported from natural cave formations in the region. Threats to M. gigas in the region are highlighted and include disturbances associated with mining and entanglement in barbed wire fences.

A late Cisuralian (early Permian) brachiopod fauna from the Taungnyo Group in the Zwekabin Range, eastern Myanmar and its biostratigraphic, paleobiogeographic, and tectonic implications

2021 ◽  
pp. 1-31
Author(s):  
Hai-peng Xu ◽  
Kyi Pyar Aung ◽  
Yi-chun Zhang ◽  
G.R. Shi ◽  
Fu-long Cai ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Cold Water ◽  
Water Environment ◽  
Climatic Conditions ◽  
Early Permian ◽  
The North ◽  
Southern Thailand ◽  
Brachiopod Fauna ◽  
Insight Into ◽  
Different Parts

Abstract The tectonic evolution of the Sibumasu Block during the Permian remains controversial, and Permian faunas and their paleobiogeographic affinities provide some insight into its paleogeographic and tectonic evolutionary histories. In this paper, a new brachiopod fauna dominated by Spinomartinia prolifica Waterhouse, 1981 is described from the uppermost part of the Taungnyo Group in the Zwekabin Range, eastern Myanmar. This brachiopod fauna includes 23 species and its age is well constrained as late Kungurian by the associated conodonts, i.e., Vjalovognathus nicolli Yuan et al., 2016 and Mesogondolella idahoensis (Youngquist, Hawley, and Miller, 1951), contrary to the late Sakmarian age given to the same brachiopod faunas previously reported from southern Thailand and Malaysia. Based on comprehensive comparisons of the Cisuralian brachiopod faunas and other data in different parts of the Sibumasu Block, we consider that they are better subdivided into two independent stratigraphic assemblages, i.e., the lower (earlier) Bandoproductus monticulus-Spirelytha petaliformis Assemblage of a Sakmarian to probably early Artinskian age, and the upper (younger) Spinomartinia prolifica-Retimarginifera alata Assemblage of a late Kungurian age. The former assemblage is a typical cold-water fauna, mainly composed of Gondwanan-type genera, e.g., Bandoproductus Jin and Sun, 1981, Spirelytha Fredericks, 1924, and Sulciplica Waterhouse, 1968. The latter assemblage is strongly characterized by an admixture of both Cathaysian and Gondwanan elements, as well as some genera restricted to the Cimmerian continents. Notably, the spatial distribution pattern of these two separate brachiopod assemblages varies distinctly. The Sakmarian cold-water brachiopod faunas have been found in association with glacial-marine diamictites throughout the Sibumasu Block including both the Irrawaddy and Sibuma blocks. In contrast, the Kungurian biogeographically mixed brachiopod faunas are only recorded in the Irrawaddy Block, unlike the Sibuma Block that contains a contemporaneous paleotropical Tethyan fusuline fauna. Thus, it appears likely that by the end of Cisuralian (early Permian), the Sibumasu Block comprised the Irrawaddy Block in the south with cool climatic conditions, and the Sibuma Block in the north with a temperate to warm-water environment, separated by the incipient Thai-Myanmar Mesotethys.

scholarly journals Lithostratigraphy and late Cenozoic fluvial styles of Siwalik Group along Kankai River section, East Nepal Himalaya

1970 ◽  
Vol 12 ◽  
pp. 63-74 ◽  
Author(s):  
Prakash Das Ulak
Keyword(s):  
Grain Size ◽  
River Section ◽  
Late Cenozoic ◽  
Nepal Himalaya ◽  
Fine Grained ◽  
The North ◽  
Lithostratigraphic Units ◽  
Facies Associations ◽  
Siwalik Group ◽  
Southern Flank

This paper describes on lithostratigraphy as well as evolution of the fluvial styles in late Cenozoic Siwalik Group along the Kankai River section of east Nepal Himalaya. The Siwalik Group lies on the southern flank of the Himalaya, is composed of molasse sediments, which were derived from the rising Himalaya in the north. The group along the Kankai River section is lithologically divided into the Lower, Middle and Upper Siwaliks, in ascending order based on increasing grain size and lithology. The Lower Siwaliks is subdivided into the lower and upper members, whereas the Middle Siwaliks is subdivided into the lower, middle and upper members on the basis of the relative thickness of the sandstone and mudstone beds, frequency of occurrence of these beds, and grain size of sandstone. The Upper Siwaliks is subdivided into the lower and upper members based on the clast size in conglomerate and constituent of the Siwalik sandstone boulders in conglomerate. Based on the lithology, assemblages of sedimentary structure and sediment body architectures, seven facies associations (FA1 to FA7) are recognised. These facies associations are closely related to each lithostratigraphic units of the area. The sediments of the lower and upper members of the Lower Siwaliks are products of the fine-grained meandering and flood flow-dominated meandering systems, respectively. The lower, middle and upper members of the Middle Siwaliks are interpreted as the deposits by sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of gravelly braided to debris flow-dominated braided systems, respectively.   doi: 10.3126/bdg.v12i0.2251 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 63-74

Occurrence and genetic implications of hyalophane in manganese-rich iron-formation, Cuyuna Iron Range, Minnesota, USA

1994 ◽  
Vol 58 (392) ◽  
pp. 387-399 ◽  
Author(s):  
Peter L. McSwiggen ◽  
G. B. Morey ◽  
Jane M. Cleland
Keyword(s):  
Depositional Environment ◽  
Iron Formation ◽  
East Central ◽  
Early Proterozoic ◽  
Iron Range ◽  
The North ◽  
History Of ◽  
Ferromanganese Deposits ◽  
Iron Formations ◽  
Chemical Sediments

AbstractThe recent discovery of hyalophane [(K,Ba)Al1−2Si3−2O8] on the North range segment of the Early Proterozoic Cuyuna Iron Range of east-central Minnesota has shed new light on the depositional environment of these rocks. This Ba-feldspar occurs in a 10 m thick interval within the main iron-formation and typically contains between 8 and 26 mol.% celsian (BaAl2Si2O8). Its occurrence in several textural settings suggests that barium was being deposited at various stages in the paragenetic history of the iron-formation. Some of the hyalophane grains occur as the cores of micronodules, which are structurally similar to oolites or oncolites, but mineralogically are very complex. The hyalophane also occurs as rims on core grains of diverse mineral composition and as discrete phases in late crosscutting veins.Hyalophane, like other Ba-silicates, has a very restricted paragenesis. They are associated typically either with sedimentary manganese and ferromanganese deposits, or with Cu-Pb-Zn-Ba deposits. The presence of hyalophane in the Early Proterozoic manganiferous iron ores of east-central Minnesota casts doubt on the historic interpretation of these deposits as typical Superior-type sedimentary iron-formations and instead supports the view that these deposits, at least in part, consist of chemical sediments from a hydrothermal fumarolic system. The suggested involvement of a hydrothermal system is also supported by the occurrence of aegirine within the hyalophane-rich layer, and the occurrence of tourmalinites and Sr-rich baryte veins elsewhere in the Cuyuna North range.

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